Abstract
Previous research has shown that prior adaptation to a spatially circumscribed oscillating grating results in the duration of a subsequent stimulus presented within the adapted region being underestimated (Johnston et al, 2006; Burr et al, 2007). Recent work using unidirectional stimuli has shown direction-contingent duration compression, which suggests that the underlying adapted mechanisms are cortical in origin (Curran & Benton, 2012). However there is still some disagreement regarding whether adaptation-induced duration compression is retinotopic or spatiotopic. We addressed this question by having participants adapt to a unidirectional (upwards) random dot kinematogram, and then measuring perceived duration of a 600ms test dot pattern located in either the same retinotopic or the same spatiotopic location. The adaptor stimulus (6.3 deg diameter) was centered 4.2 deg and 3.5 deg to the right and above fixation, respectively. Initial adaptation lasted 30s, with subsequent top up adaptor stimuli being presented for 5s. Prior to each test phase the fixation spot was shifted 7.6 deg to the right. In the retinotopic condition the test and adaptor retinal coordinates were identical, and in the spatiotopic condition the test and adaptor spatial coordinates were identical. The test stimuluss motion direction was either identical or opposite to the adaptor. The comparison stimulus was centered 4.2 deg and 3.5 deg to the right and below fixation, respectively, and moved in the opposite direction to the test stimulus. Presentation order of the test and comparison stimuli was randomised from trial to trial. While significant direction-contingent duration compression was observed when the adaptor and test stimuli appeared in the same retinotopic location, we found no evidence for spatiotopic duration compression. Our finding demonstrates the involvement of retinotopic-tuned, but not spatiotopic-tuned, cortical mechanisms in the timing of subsecond visual events.
Meeting abstract presented at VSS 2014